1. Field of the Invention
The present invention relates generally to three-dimensional (3-D) models and, in particular, to a method and apparatus for obtaining imaging device orientation information through analysis of test images.
2. Background Information
Creating three-dimensional (3-D) models of objects allow the models to be viewed from many different angles unlike two-dimensional (2-D) models that may only be viewed from one angle. One method of creating 3-D models is to take a multitude of images of real objects from different positions and exploit the differences in the objects' projection. These multitude of images may be suitable to produce 3-D models of the object. Once a 3-D model is produced, the 3-D model could be placed in a virtual world and may be shared with others, much like photos or TV. In particular, the commercial viability of 3-D models is remarkably pronounced in the entertainment, advertisement, and simulation industries.
The multitude of images may be captured using an imaging device such as a camcorder or a digital camera, for example, in a 3-D imaging device system. However, before any images may be captured for 3-D modeling, the position and orientation of each imaging device should be determined. This determining procedure is known as calibration. The reason for the calibration is that the computer used to create the 3-D data must know the relative position of the imaging devices with respect to a coordinate system (e.g. Cartesian, polar, etc.), which may be arbitrarily positioned in space, so that each coordinate image point of the captured image of one imaging device may be correlated with an image point in the captured image of the other imaging device. Through this correlation, the location of features of the 3-D object may be determined in the chosen coordinate system. In other words, X, Y, Z coordinates of the features of the target object may be determined corresponding to points in 3-D space which is the 3-D data.
One calibration method could be mechanically positioning the imaging devices on to a calibrated bar fixture with known fixed points so that once positioned, the imaging devices are calibrated. However, this method would require highly sophisticated calibrating equipment and an expensive calibrated bar. This is due to the high degree of accuracy required in a 3-D imaging device system. Further, a highly trained personnel would be required to make such adjustments. Additionally, due to the requirement that the calibration must be precise, such calibration would have to be performed in the factory and once calibrated, the position of each imaging device must remain unaltered.
This method is cumbersome in that when the user desires to adjust the distance between the imaging devices, for example, to take a stereoscopic image of a small object or a large object, the user is unable to do so because the user does not have the sophistication to make the calibration after the adjustment. Further, if the 3-D imaging device system is subjected to some knocking (shock, etc.) or mechanical manipulation that de-aligns the imaging devices, the system would be required to be returned to the factory or authorized dealer for recalibration with suitable equipment and methods, possibly at great expense. This results in the loss of usage and frustration to the user. Furthermore, in mechanically calibrating the imaging devices, it is assumed that the photosensitive area (i.e. image sensor) is properly aligned with the imaging device. However, many times, the image sensor may not be aligned resulting in the mechanically well aligned imaging device to be mis-aligned accordingly. Therefore, what is needed is a method and apparatus of calibrating the 3-D imaging device system that can be performed with ease by the user and overcomes the shortcomings of the method described above.